1. Field of the Invention
The present invention relates to a high-voltage transformer used for a lighting circuit of a backlight discharge lamp on a liquid crystal display panel, and more particularly, to a double transformer type high-voltage transformer which integrates two transformer sections in a single body.
2. Description of the Prior Art
Conventionally, a transformer for a backlight of various types of liquid crystal display panel used for a notebook personal computer, etc., capable of simultaneously discharging and lighting a plurality of cold cathode discharge lamps (hereinafter referred to as “CCFL”) is known. Using a plurality of CCFLs can meet demands for enhanced brightness and uniform illumination etc., of a liquid crystal display panel.
As this type of circuit for lighting CCFLs, an inverter circuit which transforms a DC voltage of approximately 12 V to a high-frequency voltage of approximately 2000 V at 60 kHz using a high-voltage transformer and starts discharging is generally used.
It should be noted that since such a high-voltage transformer (inverter transformer) is mounted on a board and set in a predetermined space such as a liquid crystal display panel apparatus, there is a demand for a drastic reduction in size and profile in response to requests for a smaller and slimmer liquid crystal display panel apparatus, etc. Furthermore, in order to promote the downsizing of the apparatus, there is also a strong demand for the development of a technology which allows a single high-voltage transformer to light a plurality of CCFLs.
As a conventional high-voltage transformer capable of lighting a plurality of CCFLs, an inverter transformer having an open magnetic circuit structure described in Japanese Unexamined Patent Publication No. 2001-267156 is known. The inverter transformer described in Japanese Unexamined Patent Publication No. 2001-267156 is provided with a plurality of bar-like magnetic cores formed independently for a common primary winding with each of the plurality of bar-like magnetic cores wound with a secondary winding so as to light the plurality of CCFLs.
However, the transformer described in Japanese Unexamined Patent Publication No. 2001-267156 mentioned above has the primary winding common to the plurality of secondary windings and if, for example, a load of one CCFL fluctuates, outputs to other CCFLs also fluctuate. Furthermore, even CCFLs of the same specification have variations in their characteristics and use of such a common primary winding results in unstable lighting of other CCFLs because of variations in their individual characteristics.
Furthermore, the transformer described in Japanese Unexamined Patent Publication No. 2001-267156 uses a common primary winding and requires only a small number of working steps and has apparently excellent operability, but at least the primary winding must be provided after a plurality of bobbins have been assembled, which makes winding on tiny high-voltage transformers difficult and contrarily reduces the work efficiency as a whole.
Japanese Unexamined Patent Publication No. HEI 10-208956 discloses a high-voltage transformer having a closed magnetic circuit structure integrating two transformer sections into one body, but even if outputs are supplied to two CCFLs independently, magnetic interference is produced and it is difficult to actually operate them as double transformers. That is, the transformer described in this Publication is intended to obtain a high current capacity and low DC resistance by connecting the winding start tip and winding end tip of the two secondary windings and has a structure and object totally different from those of the present invention.
The present invention has been implemented in view of the above described circumstances and it is an object of the present invention to provide a high-voltage transformer capable of simultaneously driving a plurality of loads with a single high-voltage transformer, of an independent output type which prevents fluctuations of each load from affecting the driving of other loads and capable of avoiding any reduction in the efficiency of winding operation.